/Engine/Source/Developer/FunctionalTesting/Public/AutomationBlueprintFunctionLibrary.h
Sets all viewports of the first found level editor to have the VisualizeBuffer ViewMode and also display a given buffer (BaseColor/Metallic/Roughness/etc.)
static void SetEditorViewportVisualizeBuffer ( [FName](API\Runtime\Core\UObject\FName) BufferName )